How To Install

I recommend that a competent mechanic perform this suspension conversion. There are no permanent modifications required and this is a truely bolt on kit.

How to install the spring conversion kit:

1) Unbolt the two lower SLS shock bolts, one upper bolt located under the interior carpet (secured with phillips screws) and the hydraulic lines to remove the SLS struts from both sides.

2) I have found it is easiest to use a high quality automotive spring compressor to compress the coil springs to remove them and install the new replacement coil springs.

OR

Unbolt the two large bolts towards the front of the control arms where it attaches to the sub frame. (Be careful not to cross thread these bolts upon re-installation) They must be re-torqued to spec also. They will need to be loosened if you do not have the correct spring compressor.

3) Clean the spring perches and install the new springs (be sure to leave the factory round rubber boot in the perches to cut down on spring creep noise). The installed rubber end of the new spring also goes into the spring perch. Do not remove the rubber isolator on the spring end! This is installed to cut down on spring creep noise.

4) Install the new shocks and hardware with the dog bone and two bolts into the control arm and the threaded shock rod into the floor. If not using the Sensen shocks with the complete kit, you can purchase Bilstein shocks for any W123 1976-1985 300D sedan.

Disabling the SLS System: I recommend that you remove all the remaining SLS components such as the supply lines, accumulators, bottle, and pump on the engine. If you do not disable the pump, it will eventually pump out all fluid, seize and could cause damage to the engine.

There are two ways to disable the pump:

1) Remove the engine mounted SLS pump and remove the small round metal drive connector that mates the camshaft and the SLS pump. This piece has a "cross" milled in the middle of it. Once this piece is removed, the pump will no longer turn. Finally, clean the gasket surface and reinstall the pump with a new gasket or silicone.

OR

2) Purchase the Block off Plate kit and remove the pump altogether. This is a much better option which will allow you to remove the hoses, pump, and tank from the engine compartment which will give you more room to work on your engine and decrease weight. Remove the SLS pump from the engine and the round connector piece. Clean the engine gasket surface and install a small bead of the provided silicone where the gasket was located. Install the new block off plate with the bolts provided. (BEST OPTION)

It is a good idea to check and replace any worn suspension control arm bushings and retighten all control arm/subframe bolts at this time and test drive.

I recommend that a competent mechanic perform this suspension conversion. There are no permanent modifications required and this is a truly bolt on kit.

How to install the SLS conversion kit:

1) Remove tires and jack up rear of vehicle. Be sure to use safety stands in factory recommended locations. Remove the lower plastic control arm covers. Unbolt the two lower SLS strut bolts. Remove rear seats and interior panels to access the one upper bolt located under the interior carpet. Remove the rubber hydraulic lines and then remove the SLS struts from both sides of vehicle.

2) Using a ½” drill bit, drill out the ¼” drain hole on the bottom of the lower control arm which will accept the new mounting system, Remove the upper bolt of the sway bar links and move them to to outside of the sway bar - this allows extra room of the new shocks - if this is not completed, as the suspension moves, the sway bar link can hit the new shocks and damage them. Its possible that 4Matic equipped vehicles do not allow the use of the sway bar with the SLS conversion.

3) Install the lower portion of the pre-assembled replacement SLS “air” shock. Place the lower bracket stud though the new ½” hole in the lower control arm. Secure lower using a lock-washer and nut. Place large washer and rubber bushing on the top shock mount and feed though the car body. Be sure that threaded air hose fitting on the shock faces the tire. Go to the inside of the vehicle and place a second rubber bushing, flat washer, and nut on the top shock mount and tighten. Use hacksaw or die grinder to cut off the excess stud from the top shock mount to allow carpet to sit flat (or remove piece for easy access to shock mounts)

4) Go to other side of vehicle and repeat steps1-35) Disabling the SLS System: All of the SLS lines, supply bottle and other components can be left on the vehicle just in case you decide to return the vehicle to stock configuration. The SLS pump on the w124 vehicles is incorporated into the power steering pump. To disable the SLS function of the dual pump, simply replace the banjo bolt the provided bolt into the banjo fitting (along with the brass washer off the old banjo bolt) which will not allow hydraulic fluid to be pumped into the system. If you prefer to not use this option you can loop the system by the sls valve in the rear of the vehicle so the pump can still circulate fluid. Or, you can replace your tandum pump with a non-sls power steering only pump.

6) Following the provided air shock manufacturer’s instructions for the air lines, install the air lines to the shocks. All o-rings at any connections must be wet with soapy water (important!) There are different ways to run the air lines. I recommend that using zip-ties, run the lines high and tight out of the way of the suspension components and exhaust. The best place I found for the air line’s Schrader valve is inside the rear passenger side panel. Run the hoses though the rubber body plug and out to each air shock.

7) Check to make sure all of the bolts are tight on the air shocks and sway bar links. Be sure to recheck all bolts within 50 miles of driving and periodically. Air shocks are adjustable and I typically run approximately 80lbs of compressed air in the system. You will probably use between 60-80psi. The max recommended by the manufacturer is 120lbs. The shocks will need an occasional fill as they can bleed air off with use.

It is also good idea to check and replace any other worn suspension control arm bushings and retighten all control arm/subframe bolts at this time and test drive. Your rear coil springs must be in good condition. If they are not a matching set or worn out, you could experience some sagging.